Transcript Lagomorpha, Macroscelidea, RODENTIA Mammalogy

Lagomorpha,
Macroscelidea,
RODENTIA
Mammalogy
EEOB 625
13 February 2004
Order Lagomoprpha
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Are lagomorphs closely related to Rodentia?
- similar cranial morphology & adaptive zones
- no consensus from molecular studies (Vaughan)
• Lagomorphs arose in Asia (Paleocene) underwent
radiation in N. America in Oligocene - Miocene
• Comparisons with Rodentia:
- incisors & adaptations to herbivory I: 2/1 vs. I: 1/1
- Jointed skull with diastema & fenestrated maxillary
- cursorial adaptations: long hind legs (in Leporidae)
Order Lagomorpha – 80 species
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Worldwide distribution except Australia
Family Leporidae: 11 genera, 54 species
Competitive herbivores with derived cursorial
adaptations in diverse habitats around the World
Family Ochotonidae: 2 genera, 26 species
Smaller with sorter hind limbs and ears
Nearctic and Paleactic in mountainous habitats
Unusual nutritional strategy of “hay making”
Order Macroscelidea: Elephant Shrews
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Family Macroscelididae: 4 genera, 15 species
Medium-sized, 50-500 g, in the Ethiopian since
the Miocene
Related to insectivores or elephants?
Reduction of digits to 4 in pes, & 3 (?) in pes
Wide variety of habitats, feed on a variety of
invertebrates, mostly termites & ants
Rodentia: the gnawing victors
• About 43% of all mammals are rodents
• Criteria of success of a taxon __, ___, ___
• Why are rodents so successful? (Exam II)
How do we approach such a question?
• Origin and Evolution: Fossils from the late
Paleocene in Asia and North America
- Paramys, a squirrel-like ancestral genus from
the Paleocene
Therapsid
Multituberculate
Paramys sp
Feldhamer (1999)
Rodentia: the gnawing victors
• How do we classify 2004 species, 443 genera, and
29 extant families?
• Derived characters (Vaughan Table 18-1)
• Parallel evolution obscures relationships and make
classification to suborder difficult
• A classification based on the infraorbital foramen,
masseter, & zygomatic arch (Vaughan 18-2)
• Sciuromorpha, Myomorpha, Hystricomorpha
Cobert (1969)
Paramys sp
Zygo-masseteric Patterns in Rodents
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Sciuromorphous – Primitive, squirrel-like
masseter lateralis originates on rostrum and
zygomatic plate, infraorbital foramen, small
Myomorphous – Derived, mouse-like
medial masseter originates on rostrum (maxillary)
& passes through a slightly enlarged infraorbital
foramen.
Hystricomorphous – Highly derived,
porcupine-like. Medial masseter originates on
rostrum and passes through a greatly enlarged
infraorbital Typical of several Neotropical families
Medial masseter & the
infraorbital foramen of a
myomorph rodent
Rodent Dentition & Mastication
• Is mastication the key to rodents’ success?
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Incisors: enamel on labial surface only and
rootless for continuous growth
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Diastema - a common gap in herbivores
Molars & premolars similar in appearance but
different in development.
Marvelous masticatory movements of the
mandible: the elongated glenoid fossa and the
moveable mandibular symphysis
Heteromyidae
View from below
glass of a foraging
kangaroo rat
Seeds & beads
The End
Lagomorpha,
Macroscelidea,
RODENTIA I
Family Dipodidae
• Jerboas & jumping mice (51 species)
• Nearctic, Palearctic, Ethiopian,
Dipodidae
(= Zapodidae)
Zapus or Napaeozapus ?